The present invention relates to a rotor for a rotary wing aircraft. More specifically the invention relates to a rotor structure for adjusting the blade angle movements about a respective blade angle axis in a rotary wing aircraft in which the rotor blades are secured to the rotor hub in a hingeless and bearingless manner. For this purpose the blades comprise a torsion yielding blade neck section between the blade proper and the respective hingeless and bearingless securing means.
The blade root which connects the torsion yielding neck section to the securing means is stationary as far as blade angle adjustments are concerned. The blade angle adjustment is accomplished by means of a control rod and a torsion stiff connection between the blade proper and the control rod. Such torsion stiff connection comprises a sleeve which extends in parallel to the blade neck section without touching the blade neck section.
Such a rotor is, for example, disclosed in German Patent Publication (DE-OS) No. 2,758,086. The structure of such a rotor is relatively simple because it does not require any blade hinges nor does it require any blade bearings. These features also result in a relatively small structural weight. Additionally, such rotors are capable to withstand wear and tear better than conventional rotors. Thus, the risk of damage in such rotors is low and could be further reduced by using the rotor hub as a protective housing for the blade angle or pitch angle control means as, for example, disclosed in German Patent Publication (DE-OS) No. 2,658,828. However, such construction of the rotor hub encounters the difficulty that the prior art blade control means as integrated into the rotor hub require that the blade root is rotatable relative to the respective blade securing means so that the control rods may be operatively connected to the rotor blades for the pitch angle or blade angle adjustment.
U.S. Pat. No. 4,257,738 discloses a rotor mounting assembly for rotary wing aircraft wherein the blade roots are mounted in bearings for connection to the rotor hub. This reference does not disclose any details regarding the transmission of the force necessary for adjusting the blade angle.
The German Patent Publication (DE-OS) No. 2,658,828 discloses a linkage system for the blade angle or blade pitch angle adjustment of the rotor blades in a helicopter rotor. The present invention aims at using a simpler control linkage for the blade angle adjustment.
A rotor blade or wing with a torsion yielding neck portion is disclosed in German Patent Publication (DE-AS) No. 2,806,119. Such a blade is suitable for the present purposes.